Computer hard disk drives, also known as fixed disk drives or hard drives, have become a de facto standard data storage component of modem computer systems and are making further inroads into modem consumer electronics as well. Their proliferation can be directly attributed to their low cost, high storage capacity and high reliability, in addition to wide availability, low power consumption, high data transfer speeds and decreasing physical size.
These disk drives typically consist of one or more rotating magnetic platters encased within an environmentally controlled housing that further includes all of the electronics and mechanics to read and write data and interface with other devices. Read/write heads are positioned above each of the platters, and typically on each face, to record and read data. The electronics of a hard disk drive are coupled with these read/write heads and include numerous components to control the position of the heads and generate or sense the electromagnetic fields representing data. These components receive data from a host device, such as a personal computer, and translate that data into magnetic encodings written onto the disk platters by the heads. Further, when a host device requests data from the drive, the electronics locate the desired data, sense the magnetic encodings which represent that data and translate those encodings back into the binary digital information which the host device can understand. Further, error detection and correction algorithms are applied to ensure accurate storage and retrieval of data.
One area in which significant advancements have been made has been in the area of read/write head technology and the methods of interpreting the magnetic fluctuations sensed by these heads. The read/write head, of which a typical hard disk has several, is the interface between magnetic platters and the disk drive electronics. The read/write head actually reads and writes the magnetically encoded data as areas of magnetic flux on the platters. Data, consisting of binary 1""s and 0""s, are encoded by sequences of the presence or absence of flux reversals recorded or detected by the read/write head. A flux reversal is a change in the magnetic flux in two contiguous areas of the disk platter. Traditional hard drives read data off the platters by detecting the voltage peak imparted in the read/write head when a flux reversal passes underneath the read/write head as the platters rotate. This is known as xe2x80x9cpeak detection.xe2x80x9d However, increasing storage densities require reduced peak amplitudes and better signal discrimination and higher platter rotational speeds are pushing the peaks closer together thus making peak detection more difficult to accomplish.
Magneto-resistive (xe2x80x9cMRxe2x80x9d) read/write heads have been developed with increased sensitivity to sense smaller amplitude magnetic signals and with increased signal discrimination to address some of the problems with increasing storage densities. In addition, another technology, known as Partial Response Maximum Likelihood (xe2x80x9cPRMLxe2x80x9d), has been developed to further address the problems with peak detection as densities and rotational speeds increase. Borrowed from communications technology, PRML is an algorithm implemented in the disk drive electronics to interpret the magnetic signals sensed by the read/write heads. PRML-based disk drives read the analog waveforms generated by the magnetic flux reversals stored on the disk. However, instead of looking for peak values to indicate flux reversals, PRML-based drives digitally sample this analog waveform (the xe2x80x9cPartial Responsexe2x80x9d) and use advanced signal processing technologies to determine the bit pattern represented by that wave form (the xe2x80x9cMaximum Likelihoodxe2x80x9d). This technology, in conjunction magneto-resistive (xe2x80x9cMRxe2x80x9d) heads, have permitted manufacturers to further increase data storage densities. PRML technology further tolerates more noise in the sensed magnetic signals permitting the use of lower quality platters and read/write heads which increases manufacturing yields and lowers costs.
The read/write heads of the hard disk drive are coupled with a device called a read/write channel. Herein, the phrase xe2x80x9ccoupled withxe2x80x9d is defined to mean directly connected to or indirectly connected with through one or more intermediate components. Such intermediate components may include both hardware and software based components. The read/write channel converts binary/digital data from the host device into the electrical impulses which drive the read/write head to magnetically record the data to the disk drive platters. Further, the read/write channel receives the analog waveform magnetically sensed by the read/write heads and converts that waveform back into the binary/digital data stored on the drive.
With many different drives available from multiple manufacturers, hard disk drives are typically differentiated by factors such as cost/megabyte of storage, data transfer rate, power requirements and form factor (physical dimensions) with the bulk of competition based on cost. With most competition between hard disk drive manufacturers coming in the area of cost, there is a need for enhanced hard disk drive components which prove cost effective in increasing supplies and driving down manufacturing costs all while increasing storage capacity, operating speed, reliability and power efficiency.
One area in which power efficiency can be increased is with the read/write channel of the hard drive. The read/write channel of the hard drive typically includes an analog portion, which is used to convert digital signals received from a controller to analog signals which then get sent to the read/write heads. The analog portion may also be used to receive analog signals from the read/write heads and convert them into digital signals.
Typically, the analog portion of the read/write channel 108 is manufactured using one of two methods. The first method is to use only high voltage transistors which all operate within the same voltage range. However, high voltage transistors require a lot of power, are relatively slow, and do not scale so well with a CMOS manufacturing process. The second method is to use both high voltage transistors and low voltage transistors and use a power supply voltage, which is substantially higher than the maximum rating for the low voltage transistors. Low voltage transistors operate at a higher speed, occupy less silicon area, and consume less power than high voltage transistors. Typically, low voltage transistors are used in a core area of a circuit and high voltage transistors are used in an I/O area of the circuit. However, since the high voltage transistors operate at a higher voltage range than the low voltage transistors, verification and simulations must be performed on the analog portion to insure that the low voltage transistors never receive more voltage than is required for them to operate. For example, the analog portion may include high voltage transistors that operate at a voltage range of between 2.16 volts and 2.64 volts (2.4 volts +/xe2x88x9210%), and low voltage transistors that operate at a lower voltage range, such as between 1.62 volts and 1.98 volts (1.8 volts +/xe2x88x9210%). In this example, since the analog portion is typically supplied a voltage that is within a single range, such as a voltage of 2.4 volts +/xe2x88x9210%, verification and simulations must be performed on the analog portion to insure that the low voltage transistors never receive more voltage than is required for them to operate. Moreover, additional circuitry is placed inside the analog portion to further insure that the low voltage transistors never receive more voltage than is required for them to operate. The additional circuitry, and the verification and the simulations that must be performed on the analog portion, in turn, increase the time required to design the read/write channel.
Thus, there is a need for a read/write channel which is able to operate in a single, low voltage range and accommodate a variety of transistors in order to prevent the use of additional circuitry, to eliminate additional verification and simulations performed on the analog portion, to lower the power consumption of the read/write channel, and to lower the required silicon area.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiments described below relate to a read/write channel for a hard disk drive. The read/write channel includes an analog portion and a clock synthesizer. The analog portion and the clock synthesizer both comprise high voltage transistors which operate in a first voltage range and low voltage transistors which operate in a second voltage range. The first voltage range is within the second voltage range. The read/write channel also includes a highly regulated power supply connected to the analog portion and the clock synthesizer. The highly regulated power supply supplies power that is within the first voltage range to the analog portion and the clock synthesizer.
The preferred embodiments further relate to a method for operating a read/write channel for a hard disk drive. The method includes providing an analog portion and a clock synthesizer of the read/write channel, wherein the analog portion and the clock synthesizer both comprise high voltage transistors which operate in a first voltage range and low voltage transistors which operate in a second voltage range. The method further includes insuring that the first voltage range is within the second voltage range. Also, the method includes generating power that is within the first voltage range using a highly regulated power supply and supplying the power to the analog portion and the clock synthesizer. Further aspects and advantages of the invention are discussed below in conjunction with the preferred embodiments.